There is a growing need for structures that provide personal protection against toxic chemical and biological agents. It is known to devise structures that are impermeable to toxic chemical vapors and liquids, but, when used as apparel, such structures are typically also hot, heavy and uncomfortable to wear.
The degree of comfort offered by apparel worn as a protective suit is significantly affected by the amount of water vapor that can permeate through the fabric from which the suit is made. The human body continuously perspires water as a method for controlling body temperature. When a protective fabric hinders the loss of water vapor from the body, the transpirational cooling process is hindered, which leads to personal discomfort. When a protective suit allows little or no loss of water vapor, extreme heat stress or heat stroke can result in a short period of time. Hence, it is desirable that, in addition to offering the highest levels of protection against toxic chemicals and liquids, a practical chemical and biological protective suit should have high water vapor transmission rates. It is also desirable that the appropriate protective structure be light in weight and offer the same high level of protection over a long period of time.
Co-pending U.S. patent application Ser. No. 11/593,958 relates to laminates prepared in part from continuous chitosan films. In various embodiments, the laminates are useful for fabrication as a protective article and are preferably substantially impermeable to hazardous chemical and biological agents, but sufficiently permeable to water vapor that, if worn as protective apparel, it is both protective and comfortable to wear.
The present invention provides selectively permeable laminates that contain a continuous chitosan film wherein the chitosan has been reacted with at least one polyhydroxyalkyl compound and that can be used in articles for personal protection, providing improved wearer comfort compared with impermeable articles. Such chitosan/polyhydroxyalkyl compound composite films exhibit lower shrinkage when dried, less swelling in water, and less sensitivity to dilute aqueous acid than do neat chitosan films.